Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy

Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients’ primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy

Direct determination of Ethyl Glucuronide and Ethyl Sulfate in postmortem urine specimens using hydrophilic interaction liquid chromatography–electrospray ionization-tandem mass spectometry

This work was aimed at developing and validating a hydrophilic interaction chromatography (HILIC)–electrospray ionization (ESI)-ion trap-tandem mass spectrometric method for identification and quantification of ethyl glucuronide (ETG) and ethyl sulfate (ETS) as ethanol biomarkers and at employing this method for analysis of postmortem urine samples. Analytes of interest were separated on a ZIC®-HILIC column (150 × 2.1 mm, 3.5 µm) connected to a Thermo Finnigan LCQ Deca Plus liquid chromatographic–tandem mass spectrometric instrument operated in the ESI-selected reaction monitoring mode. Seventy-nine urine case samples were divided into three groups depending on the ethanol concentration found in blood and analyzed by the developed method: group A with postmortem blood ethanol concentrations higher than 200 mg/100 mL; group B with ethanol concentrations in the range 80–200 mg/100 mL; and group C with ethanol concentrations in the range 10–80 mg/100 mL. ETG and ETS had high recoveries of 98–99%, and the HILIC column produced fine, sharp peak shapes and achieved baseline separation in less than 7 min. Both ethanol markers were detected in all groups with overall median concentrations of 100 and 23 mg/L for ETG and ETS, respectively. It can be concluded that the potential for postmortem production of alcohol increased in the low ethanol concentration group as several cases tested negative for both biomarkers in group C. ETG was detected at low concentrations in some cases for which ETS tested negative. Although ETS is stable after being subjected to many stability conditions, the use of ETS as sole evidence of alcohol ingestion may lead to a false-negative result, as we noticed in groups A and C in the present study. The use of ETG is a more reliable ethanol biomarker. Both ethanol biomarkers should be determined in heavily putrefied cases and when the ethanol concentration in postmortem blood is low

Bi-allelic Variants in IQSEC1 Cause Intellectual Disability, Developmental Delay, and Short Stature.

We report two consanguineous families with probands that exhibit intellectual disability, developmental delay, short stature, aphasia, and hypotonia in which homozygous non-synonymous variants were identified in IQSEC1 (GenBank: NM_001134382.3). In a Pakistani family, the IQSEC1 segregating variant is c.1028C>T (p.Thr343Met), while in a Saudi Arabian family the variant is c.962G>A (p.Arg321Gln). IQSEC1-3 encode guanine nucleotide exchange factors for the small GTPase ARF6 and their loss affects a variety of actin-dependent cellular processes, including AMPA receptor trafficking at synapses. The ortholog of IQSECs in the fly is schizo and its loss affects growth cone guidance at the midline in the CNS, also an actin-dependent process. Overexpression of the reference IQSEC1 cDNA in wild-type flies is lethal, but overexpression of the two variant IQSEC1 cDNAs did not affect viability. Loss of schizo caused embryonic lethality that could be rescued to 2 <sup>nd</sup> instar larvae by moderate expression of the human reference cDNA. However, the p.Arg321Gln and p.Thr343Met variants failed to rescue embryonic lethality. These data indicate that the variants behave as loss-of-function mutations. We also show that schizo in photoreceptors is required for phototransduction. Finally, mice with a conditional Iqsec1 deletion in cortical neurons exhibited an increased density of dendritic spines with an immature morphology. The phenotypic similarity of the affecteds and the functional experiments in flies and mice indicate that IQSEC1 variants are the cause of a recessive disease with intellectual disability, developmental delay, and short stature, and that axonal guidance and dendritic projection defects as well as dendritic spine dysgenesis may underlie disease pathogenesis

Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy

10.1038/s41467-020-14360-7Nature Communications11159